A composite material is a material in which at least two materials having different components or shapes as a reinforcement and a matrix are combined macroscopically so as to have a distinctive interface and effective functions. The composite material may secure various physical properties through efficient combination of each component and may be applied to various fields including aviation, space, automobiles, sports, industrial machines, medical instruments, logistics supplies, construction, and engineering materials.
A fiber reinforced composite material is manufactured using a fiber such as a glass fiber, a carbon fiber, an aramide fiber, and a silicon carbide fiber as a reinforcement, and receives much attention among composite materials, because of merits including high strength, lightweight and good moldability. Particularly, the fiber reinforced composite material is used in various uses by changing the quality of the reinforcement, the length of a fiber, etc.
Among the fibers, the glass fiber is the most widely used one as the reinforcement. For example, Korean Laid-open Patent Publication No. 2006-7004105 discloses the application of a blend of a polypropylene copolymer and a glass fiber to car articles such as a car seat, a headrest, a knee protection device, a globe box door, an instrument panel, a bumper facia, and a bumper beam, and Japanese Laid-open Patent Publication No. 2008-202013 mentions the application of a polycarbonate/styrene resin and a glass long fiber to the exterior panel of a car.
As the reinforcement other than the glass fiber, Japanese Laid-open Patent Publication No. 2011-137077 discloses a fiber reinforced composite material in which a polypropylene resin includes an organic long fiber such as a polyester fiber or a polyamide fiber so as to be used in an instrument panel of a car. Korean Laid-open Patent Publication No. 2006-0075902 discloses a fiber reinforced composite material obtained by adding a glass fiber, a carbon fiber, a graphite fiber or a metal fiber to a propylene resin with low brittleness.
A carbon fiber reinforced composite material using a carbon fiber as the reinforcement among the fiber reinforced composite material, is light and has better physical properties such as rigidity, impact resistance, heat resistance, chemical stability, dimensional stability, corrosion resistance, and flexibility than other reinforcements. The physical properties may be improved further by using a long fiber which has a long carbon fiber.
Generally, a fiber reinforced composite material may be manufactured by blending a thermoplastic resin used as a matrix with a fiber reinforcement, melting and molding by extrusion molding, etc. During molding, fibers may infiltrate between microstructures of the resin and be uniformly dispersed in the matrix as a reinforcement. In the case where a long fiber is used as the reinforcement, miscibility with the resin may be low, and the infiltration of the resin into the microstructures may not be easy, thereby rather deteriorating physical properties.
In order to stabilize interface properties between a matrix resin and a fiber for a reinforcement, various methods are known, and one of the methods uses a compatibilizer during molding. As the compatibilizer, modified polyolefine (PO) (PP-g-MA) prepared by grafting a polypropylene resin and anhydrous maleic acid (MAH) in a ratio of 9:1 is the most widely used. The compatibilizer is used irrespective of the material of the reinforcement or the matrix.
For the fiber reinforced composite material, the kind or amount of a resin used as a matrix may be changed according to the application, and accordingly, the selection of a reinforcement among a glass fiber, a carbon fiber, an aramide fiber, a metal fiber, etc. may be changed. That is, interface properties between the resin and the reinforcement may be different according to the kind of the matrix resin and the reinforcement, and sufficient physical properties may not be secured by simply applying PP-g-MA known as the compatibilizer. Further, the interface properties may be greatly influenced by the parameters of a molding process.
Therefore, an optimized compatibilizer is required to be selected according to the kind of a matrix resin and a reinforcement to secure sufficient physical properties irrespective of a molding process.